How Traits are Passed On

Have your coloring picture out, analysis & your DNA origami We’ll be hanging our DNA up! Remember to know your vocabulary…make flashcards, etc.

Hanging our DNA! You will be tying your DNA to the person sitting next to you & then hanging over the lights. 1. Hole punch at the end. 2. cut 70 cm of thread 3. tie 1 DNA to either end of the thread 4. hang DNA on the light above your desk by CAREFULLY standing on your stool and having 1 DNA on either side of the light. * this process will take a little time and will continue throughout the class until everyone is done

Introduction to heredity presentation Complete dominance punnet squares

We’ll watch a crash course to get an over view of genetics. You can also read about it in your book or many websites. You can also watch the crash course over and over It’s gonna be a lot and we’ll watch it again at then end of the unit! fFUEA fFUEA

Chromosomes Humans have 46 chromosomes 23 from mom & 23 from dad which are called homologus pairs. Each codes for hundreds to thousands of genes

Gene A gene is a segment of DNA that codes for one protein That protein can determine what trait we express (i.e. the protein for brown pigments can give us brown eyes)

Inherited Traits Homologous pairs code for the same genes, though they may have slightly different versions (i.e. one codes for brown eyes, one for green eyes) Different versions of the gene are called alleles EX: brown eye allele For every gene we have 2 alleles, which may be different or the same Homologous

You have 2 alleles for every gene type because you have 23 homologus pairs one from mom & one from dad! Each parent gave you a random set of ½ of their homologous chromosomes, these homologous chromosomes have same types of genes BUT can have different alleles.

So, you look a bit like each parent but not exactly like either because you are a mix of both of their genes.

Vocabulary Homozygous – to have 2 identical alleles Heterozygous – to have 2 different alleles HomozygousHeterozygous

So you have 2 alleles. Which determines what you look like?? It depends. This is where genetics gets really complicated We’ll start with the easiest… Complete Dominance!

Medelian genetics and humans? TRUE Mendelian Wet (dominant) or dry (recessive) earwax Ability to taste phenylthiocarbam ide (dominant) Albinism (recessive) Brachydactyly (shortness of fingers and toes) Once THOUGHT to be… Eye color Hair color Morton's toe Tongue rolling Widow's peak (allele) Detached (dominant) or attached (recessive) earlobes Hitchhiker's thumb (recessive)

True Mendelian traits are RARE in humans. Also pretty rare in general. We will look at these more complex inheritance traits in the next few days First we’ll master complete dominance! AKA Menden traits.

Complete Dominance One allele, the dominant one, completely “hides” the effects of the recessive allele (or rather the recessive just doesn’t make a protein). You either express it (you have the trait) or you don’t. You express the dominant trait if you have 1 or 2 dominant alleles. Either Homozygous DOMINANT (AA) OR Heterozygous (Aa) Only see recessive trait if have both recessive alleles Homozygouus RECESSIVE (aa)

What is the dominant trait in the picture? Yellow seeds. A heterozygote is a CARRIER of the recessive trait and can pass that recessive allele to their offspring.

The Punnett Square We can use the symbols we have learned and the idea of segregation to predict the outcomes of a cross between 2 individuals. The Punnett square is a shorthand way of finding the expected proportions of possible genotype and phenotype in the offspring of a cross. If you know the genotypes of the parents, you can use the Punnett square to predict the genotypes and phenotypes of the offspring. BEWARE! The Punnett square does not give you ACTUAL results – it is a statistical prediction of what you could EXPECT from a given cross.

Human Traits Raise your hand if you have… Dimples Free earlobes Hand clasping with left on top Mid-digital hair

Punnett Square Show the possible alleles each parent could give. This example shows an Aa (heterozygous) person mating with an aa (homozygous recessive individual) Parent 1 Parent 2

Start monohybrid crosses Mono=1 so we are looking at 1 trait with complete dominance (the simplest ones that are pretty rare and Mendel was sort of lucky sort of just looked at the ones that were “working” the way he wanted- or he just picked the ones that were working out the “right” way.) Start the worksheet with the possible crosses (do the vocab at home) so you are sure on how to do punnet sq before you leave today.